DESCRIPTION: The long-term objectives of the laboratory are to examine the biomechanical, hormonal and inflammatory events that contribute to temporomandibular (TM) joint dysfunctions. Chronic pain in the temporal region may result from pathology in the TM joint, masticatory muscles, or other sources. This condition is unusually prominent in women. In most instances, there is no effective pharmacological, surgical or behavioral treatment. Many women who seek help for TM pain have demonstrable pathology within the joint capsule. This pathology is typically a derangement of intra-articular structures referred to as anterior disc displacement. The condition is usually associated with resting pain, pain with jaw motion and limitation of motion range. The etiology of disc displacement is not known. Patients with anterior disc displacements have a history of orofacial trauma, but it is not clear why this would impact disproportionately on the female population. Potentially, increased manifestation of TM pain may be related to hormonal influences on wound repair. In the present proposal, the investigators will examine whether estrogen treatment modulates basal joint tissue composition and/or its response to traumatic injury, and whether these influences create biochemical and biomechanical conditions that favor the development of anterior disc displacement. These questions will be assessed by examination of joint tissue biochemistry (relative concentrations of collagens (types I and III), cell number (DNA), cell size (RNA/DNA ratio), tissue biomechanics (e.g., elastic stiffness, failure load) and nociceptor reactivity in the traumatized, estrogen treated goat TM joint.